#include"stdio.h"

int sum(int n);

int sum(int n)
{

		int result = 0;

		do
		{
				result += n;
		}while(n-- > 0);

		return result;
}

int main()
{

	int n,result;

	printf("请输入n的值:");
	scanf("%d",&n);

	result = sum(n);

	printf("1+2+3+..+(n-1)+n的结果是:%d\n",sum(n));
	
	return 0;
}
